I. Field
The following description relates generally to wireless communications, and more particularly to providing a mechanism for transferring a mobile device from a source enhanced node B (eNB) to a target eNB.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP LTE systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out (SISO), multiple-in-signal-out (MISO), or a multiple-in-multiple-out (MIMO) system.
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP LTE systems, orthogonal frequency division multiplexing (OFDM), localized frequency division multiplexing (LFDM), orthogonal frequency division multiple access (OFDMA) systems, and the like.
In a wireless communication system, a Node B (or base station) or enhanced Node B (eNB) may transmit data to a user equipment (UE) on the downlink and/or receive data from the UE on the uplink. The downlink (or forward link) refers to the communication link from the eNB to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the Node B. The eNB may also send control information (e.g., assignments of system resources) to the UE. Similarly, the UE may send control information to the eNB to support data transmission on the downlink and/or for other purposes. As the mobile device is moved it is desirable to switch eNBs. For example, the mobile device is in communication with a source eNB, and then the device is approaching another eNB, the target eNB, and it is desirable to handover from the source to the target. This handover is also termed herein a re-pointing.
In 3GPP LTE (Long Term Evolution) which is the name given to a project within the Third Generation Partnership Project to improve the Universal Mobile Telecommunication System (UMTS) mobile phone standard to cope with future requirements. In LTE, it is currently agreed that during eNB re-pointing the radio link control (RLC) Protocol Data Units (PDU)s will not be forwarded from the source eNB to the target eNB. Additionally the RLC can be reset at each eNB re-pointing event. By reset it is meant that any RLC Service Data Units (SDU)s that were not completely delivered by RLC at the source eNB will need to be retransmitted at the target eNB.
Since RLC operation is not continuous at eNB re-pointing, special care need be taken to avoid wasting too much radio capacity and creating potential user plane interruption during the re-pointing or transferring procedure.